In the case of ESD protection devices having a control gate, operation mode typically involves either normal mode, wherein the control gate is controlled by a bias voltage to define an active clamp, or snapback mode based on punch-through effect, which occurs when the forward blocking voltage is reached.
Apart from these control gate devices, some ESD protection solutions make use of Zener diodes, which operate in avalanche breakdown mode.
However the use of Zener diodes becomes problematic when dealing with ESD protection of high voltage, fast switching devices such as fast switching voltage regulators, which during normal operation display switching times in the range of 10 ns-200 ps. Thus they can have switching times that are faster than the ESD rise time (10 ns for HBM pulse).
Not only is it difficult to provide a high voltage Zener diode that is suited for such high voltage node ESD protection, they rely on passive switching due to a triggering voltage that exceeds the forward blocking voltage. Thus it is difficult to provide a Zener diode with the desired breakdown characteristics and which avoids being triggered under normal high speed, high voltage operation.
The present invention seeks to provide a diode ESD protection solution for high voltage, high speed applications.